# Anisotropic surface potentials induced by competitive ion adsorption enable the synthesis of branched cubic Pt mesocrystals

## TL;DR

Researchers discovered that changing ion adsorption can control how platinum nanoparticles assemble, creating branched cubic structures.

## Contribution

The study introduces a new method using competitive ion adsorption to control nanoparticle assembly through time-dependent surface potentials.

## Key findings

- Pt nanoparticles first assemble at {100} facets to form a cubic core.
- Later, ion adsorption shifts attachment to {111} facets, promoting branch formation.
- Anisotropic surface potentials create electrostatic torques that align particles before attachment.

## Abstract

Creation of complex nanostructured materials through oriented attachment (OA) requires the manipulation of interparticle forces, including electrostatic repulsion, which depends strongly on surface potentials and can be modified through the effect of solution environment on interfacial chemistry. Here we show that time-dependent anisotropies in surface potential driven by competitive ion adsorption can alter facet-selectivity during OA. This phenomenon enables the synthesis of branched cubic Pt mesocrystals. Initially, Pt nanoparticles attach preferentially at their {100} facets to form a well-defined cubic core. Over time, changes in ion adsorption shift the attachment preference to the {111} facets, promoting branch formation. In both stages, anisotropic surface potentials generate electrostatic torques that align the particles prior to attachment. These findings demonstrate a generalizable strategy for directing the architecture of nanomaterials through time-resolved control of interfacial chemistry during OA, offering new pathways for the design of complex mesoscale structures.

Nanocrystal assembly is key to creating complex architectures. Here, the authors show that tuning competitive ion adsorption alters anisotropic surface potentials and electrostatic torques, directing facet attachment to enable alternative mesoscale designs.